高速進展き裂の分岐の瞬間におけるき裂先端応力場の測定

概要

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Stress field in the vicinity of fast propagating crack is measured just before and just after crack bifurcation. Cracks are of opening mode and propagate in PMMA specimens at a speed more than 600 m/s. Interferometry is applied to measure the stress field around the crack tips. High-speed holographic microscopy is used to take three successive photographs of cracks and interference fringes with high spatial resolution of 180 lines/mm. The measurement results show that the neartip stress field deviates from the K-field not only after crack bifurcation but also before bifurcation. This fact indicates that the near tip field at bifurcation is affected both by micro cracks or attempted branches around the crack tips and by the higher-order terms of stress field. And it can explain the experimental result that the bifurcation angle depends on specimen's shape and experimental conditions.
2000-05-25